Multi-stage gas compressing apparatus

ABSTRACT

A multi-stage gas compressing apparatus comprises a primary gas compressor and a secondary gas compressor. A gas compressed in the primary gas compressor is transferred to the secondary gas compressor in which the gas is further compressed. A detector detects upper and lower limits of discharge pressure from the secondary gas compressor, and a signal is sent from the detector to a control device connected to the primary and secondary gas compressors. Then, the primary and secondary gas compressors are started or stopped by the control device.

BACKGROUND OF THE INVENTION

The present invention relates to a multi-stage gas compressing apparatus for compressing a compressed gas by a plurality of compressors, and particularly relates to a multi-stage gas compressing apparatus for simplifying operation of a primary gas compressor and a secondary gas compressor.

In FIG. 5, a conventional gas compressor comprises a low-pressure primary gas compressor 101 such as a scroll compressor for compressing a compressed gas, and a high-pressure secondary gas compressor 102 or booster compressor such as a reciprocating compressor for further compressing gas compressed by the scroll compressor 101. High pressure gas compressed by the secondary gas compressor 102 is stored in a storage tank 103.

To control operation of the compressors, pressure sensors 104,105 for setting upper-limit pressure and lower-limit pressure respectively are provided to the gas compressors 101,102 respectively. Based on the upper-limit pressure and lower-limit pressure of discharge pressure detected by the pressure sensors 104,105 respectively, the primary gas compressor 101 and the secondary gas compressor 102 start and stop independently by control devices 106,107.

However, in the multi-stage gas compressing apparatus, to control each of the gas compressors 101,102 independently, it is required to provide the two pressure sensors 104,105 and the control devices 106,107. Furthermore, to adjust load, a receiver tank 108 has to be provided between the primary gas compressor 101 and the secondary gas compressor 102.

Specifically, if the primary gas compressor 101 stops, the secondary gas compressor 102 only runs. So the secondary gas compressor 102 is loaded excessively and is liable to be out of order.

The whole apparatus becomes not only more complicate, but also high cost for manufacturing it.

SUMMARY OF THE INVENTION

In view of the disadvantages in the prior art, it is an object of the present invention to provide a multi-stage compressing apparatus in which an operation control system is simplified, its cost is reduced and safety is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the first embodiment of a multi-stage compressing apparatus according to the present invention.

FIG. 2 is a block diagram of the second embodiment thereof.

FIG. 3 is a block diagram of the third embodiment when a primary gas compressor only works.

FIG. 4 is a block diagram of the third embodiment when the primary gas compressor does not work.

FIG. 5 is a block diagram of a conventional multi-stage gas compressing apparatus.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, a multi-stage gas compressing apparatus according to the present invention comprises a primary gas compressor 1 or a low-pressure scroll compressor for compressing a compressed gas; and a secondary gas compressor 3 or a high-pressure reciprocating compressor for further compressing the compressed gas, connected to the primary gas compressor 1 via a conduit 2.

High-pressure compressed gas compressed by the secondary gas compressor 3 is stored in a storage tank 5 connected to the secondary gas compressor 3 via a conduit 4.

A pressure sensor 6 is provided to the storage tank 5 to detect discharge pressure of the high-pressure gas compressed by the secondary gas compressor 3. The pressure sensor 6 is set to turn off at 1.0 MPa of the upper limit pressure and turn on at 0.8 MPa of the lower limit pressure.

When the pressure sensor 6 detects the upper limit pressure, it transmits a signal “off” to the control device 7, which transmits a signal for stopping to the primary gas compressor 1 and the secondary gas compressor 3 to stop them at the same time.

Air in the storage tank 5 is consumed and the pressure sensor 6 detects the lower limit pressure. A signal “on” is transmitted from the pressure sensor 6 to the control device 7, which transmits a signal for starting to the primary gas compressor 1 and the secondary gas compressor 3 to start them at the same time.

FIG. 2 is a block diagram of the second embodiment of a multi-stage gas compressing apparatus according to the present invention.

A relief valve 11 is provided at a conduit 10 between a primary gas compressor 8 and a secondary gas compressor 9. If the secondary gas compressor 9 is out of order or does not work, the primary gas compressor 8 will have to compress a gas to substantially the same pressure that the secondary gas compressor 9 could achieve compression. So the primary gas compressor 8 would be subjected to excessive load and would be broken. To avoid such situation, gas that flows through the conduit 10 is released to air by opening the relief valve 11, if gas pressure reaches an upper limit such as 0.75 MPa.

In the third embodiment in FIG. 3, instead of the relief valve 11, at the conduit 10 between the primary gas compressor 8 and the secondary gas compressor 9, an intermediate control device 12 is provided and comprises a pressure sensor 13 and a micro computer circuit 14. In the intermediate control device 12, upper limit pressure and lower limit pressure are set. A pressure switch may be used instead of the pressure sensor 13. The pressure sensor 13 detects pressure of gas through flowing the conduit 10 and actuates the microcomputer circuit 14 connected to the pressure sensor 13 electrically.

In FIG. 3, if the secondary gas compressor 9 is out of order or does not work, the primary gas compressor 8 will have to compress gas to substantially the same pressure that the secondary gas compressor 9 could achieve compression. The primary gas compressor 8 would be subjected to excessive load and would be broken. To avoid such situation, if the pressure sensor 13 detects an upper limit pressure such as 0.75 MPa, the microcomputer circuit 14 will transmit a signal to the primary gas compressor 8, which will stop.

In FIG. 4, if the primary gas compressor 8 is out of order or does not work, the secondary gas compressor 9 will be subjected to excessive load and will be broken as well. In order to avoid such situation, if the pressure sensor 13 detects a lower limit pressure such as 0.5 MPa, the microcomputer circuit 14 will transmit a signal to the secondary gas compressor 9, which will stop.

The range between the upper and lower limit pressures detected by the relief valve 11 or additional control device 12 are set to be lower than the range between the upper and lower limit pressures detected by the pressure sensor 5 attached to the storage tank 5. If not so, either of the primary and secondary gas compressors will be likely to be out of order.

The foregoing merely relates to embodiments of the present invention. Various changes and modifications may be made by a person skilled in the art without departing from the scope of claims. 

1. A multi-stage gas compressing apparatus comprising: a primary gas compressor compressing a gas; a secondary gas compressor connected to the primary gas compressor via a conduit and further compressing the gas compressed by the primary gas compressor; a storage tank connected to the secondary gas compressor and storing gas further compressed in the secondary gas compressor; a detector connected to the storage tank and detecting a first upper limit pressure or a first lower limit pressure of the gas in the storage tank to generate a signal; and a control device connected to the detector, the primary gas compressor and the secondary gas compressor, the signal from the detector being transmitted to the control device to start and stop the primary gas compressor and the secondary gas compressor at the same time.
 2. A multi-stage gas compressing apparatus of claim 1 wherein the detector comprises a first pressure sensor.
 3. A multi-stage gas compressing apparatus of claim 1, further comprising a relief valve at the conduit between the primary gas compressor and the secondary gas compressor, compressed gas being released through said relief valve if discharge pressure from the primary gas compressor exceeds a second upper limit pressure lower than the first lower limit pressure when the secondary gas compressor does not work.
 4. A multi-stage gas compressing apparatus of claim 1, further comprising an intermediate control device at the conduit between the primary gas compressor and the secondary gas compressor, the intermediate control device comprising a second pressure sensor and a microcomputer circuit, the primary gas compressor being stopped by the microcomputer circuit if the second pressure sensor detects a second upper limit pressure of gas flowing through the conduit when the secondary gas compressor does not work, the second upper limit pressure lower than the first lower limit pressure.
 5. A multi-stage gas compressing apparatus of claim 1, further comprising an intermediate control device at the conduit between the primary gas compressor and the secondary gas compressor, the intermediate control device comprising a second pressure sensor and a microcomputer circuit, the secondary gas compressor being stopped by the microcomputer circuit if the second pressure sensor detects a pressure less than a second lower limit pressure of gas flowing through the conduit when the primary gas compressor does not work, the second lower limit pressure being lower than the first lower limit pressure. 